A plug is designed, by insertion into an insert or socket, to make the electrical connection between electrical lines present on the one hand in the plug and on the other hand in the insert. During this insertion, plates of the plug come to bear on respective corresponding or homologous contacts of the insert. The electrical lines and the parallel plates being close together, electromagnetic induction effects cause crosstalk, i.e. interference with signals on one line by signals on adjacent lines.
In order to minimize crosstalk, twisted pairs are used in cables used to transmit data in telephone and information technology networks, for example. However, one type of local crosstalk, said “line termination”, or NEXT (Near End CrossTalk), remains present.
At high frequencies, a capacitance effect between the parallel plates of the plug causes what is called “near-end crosstalk”.
To reduce this interference, the RJ45 CAT6A standard, which concerns 10 Gbit/s networks, imposes near-end crosstalk isolation, namely:                near-end crosstalk isolation at 100 MHz: 54 dB,        near-end crosstalk isolation at 250 MHz: 46 dB, and        near-end crosstalk isolation at 500 MHz: 37 dB.        
An RJ45 connector is a physical interface often used to terminate twisted-pair cables. It includes eight electrical connection pins.
The ISO IEC 11801 standard (amendment 1 and amendment 2, in process) defines the performance of a transmission channel.
The document U.S. Pat. No. 5,547,405 describes means for reducing crosstalk on the side of the insert. Thus this document provides in an insert including four contacts a lateral extension (114) starting from the first contact (B) and passing in front of the second (A) to lie in front of the third (C). The capacitance created between the third and fifth contacts compensates the capacitance of the plug causing the crosstalk. Similarly, a lateral extension (124) starts from the fourth contact (D), passes in front of the third (C) and lies in front of the second (B) to produce compensation capacitance there. In the case of an insert including eight contacts (see FIGS. 8 and 9 of the present application), the above document has four compensation capacitances (16A, 16B, 16C and 16D) formed in the same manner by lateral extensions 3 and 6 on either side of the third and sixth contacts.
This technical solution has numerous drawbacks. As shown in FIG. 8 of the above document, it causes respective stray inductances Lp3 and Lp6 in the fine connections that link the contact to each of its lateral extensions, which adds crosstalk between the signals, notably inductive crosstalk. Moreover, these fine connections and the contact that they cross form stray capacitances which increase the crosstalk between the signals.
The document US 2002/0081908 concerns a low-crosstalk insert. As shown in FIGS. 15a to 17 of that document, the second preferred embodiment includes two half-inserts (120a and 120b) separated by a layer (142) of air that surrounds on the one hand the even-numbered conductors (120a) and on the other hand the odd-numbered conductors (120b).
In each of these half-inserts, capacitances are formed between three conductors (T2, T3, T4 and R1, R3, R2) because of local deformations of the conductors called “protrusions”. As shown in FIG. 17, the central conductor (T3, R3) has two lateral extensions that face respective lateral extensions of the other conductors.
However, because of the 8-shaped central contact, an unwanted inductive effect is produced on each of the connections between the lateral extensions. The third embodiment of the above document seeks to reduce these inductive effects.
The present invention aims to remedy the above drawbacks.